1. Field of the Invention
The present invention relates to an ink, and more particularly, to an ink jet recording ink. The present invention pertains to a water based ink capable of providing blue images with improved indoor discoloration, and an ink jet recording method employing such a ink.
2. Description of the Related Art
Conventionally, water based inks of the type in which a water soluble dye is dissolved in a water carrier medium have been used as inks for fountain pens and felt pens and as inks for use in the ink jet recording. A water soluble organic solvent is generally added to such water based inks in order to prevent clogging of a pen point or an ink ejecting nozzle.
The conventional inks are required to provide images having a sufficient density, not to cause clogging of a pen point or a nozzle, to dry quickly when placed on a recorded material, to bleed less, to exhibit excellent storage particularly when it is used in the ink jet process which utilizes heat energy, and to provide images which exhibit excellent light fastness and water fastness.
Among the above requirements of the conventional inks, durability of the images formed by them is particularly important.
Conventionally, durability of the images has been mainly brought into question in the form of color fading of the images caused by the direct sunshine or various types of light, and this problem involving the color fading has been solved by the selection of dyes which exhibit excellent light fastness. For example, C.I. Direct Blue 86, whose skeleton is composed of phthalocyanine, has been conventionally employed as the dye for blue inks.
However, in addition to the color fading caused by high illumination, color fading of the images caused in an indoor environment has been drawing attention in recent years.
This type of color fading occurs in an indoor environment which is not reached by direct sunshine, and certain types of recorded materials on which images are formed accelerate this color fading. The use of the widely used C.I. Direct Blue 86 cannot solve this problem.
Particularly, these types of color fading occur to a great extent with the so-called coated paper on which an ink accepting layer composed of a pigment and a binder is formed on a substrate such as paper to enhance coloring and vividness of the ink and to improve image quality, such as definition. Selection of dyes exhibiting excellent light fastness alone is not enough to solve this problem.